1. Field of the Invention
This invention relates to a doctor device for metering and/or equalizing a liquid-to-pasty medium applied to a running surface, wherein in the case of direct application the surface is a running paper web, paperboard web or other fibrous web and in the case of indirect application a transfer element which transfers the application medium to the fibrous web. The doctor device has a holder arranged on a support beam for accommodating a doctor element used for the metering and/or equalizing.
2. Description of the Related Art
Doctor devices of this type are used in conjunction with applicators which, as previously mentioned, are suitable for direct or indirect application. The liquid or pasty medium for application is applied onto the fibrous web by way of a pressurized compartment with the help of a doctor element constructed as a doctor rod, a doctor bar or a doctor blade for example. Also known are doctor devices for use in finish-metering devices, with which a layer of liquid or pasty medium previously applied to the fibrous web is finish-metered to a predefined quantity. The finish-metering is performed likewise by way of one of the above mentioned doctor elements. However, the doctor device can also be used solely to even out, meaning equalize, the medium previously applied in the required quantity.
In the case of conventional applicators or finish-metering devices the doctor element is fastened with the help of comparatively complex constructional solutions. The geometrically correct seating of the doctor element, for example a doctor blade, is assured with a system of guide bars, support bars, clamping bars and pressure bars. On conventional constructions the numerous bar elements and additional components are screwed together. The known constructions thus have very many individual parts which are exposed on the one hand to a high temperature and on the other hand directly to the coating medium and require a corresponding assembling and dismantling effort in order to clean the doctor device.
From DE 9109785 U1 there is known a doctor device with a holding bar for accommodating a doctor blade, wherein the holding bar in the direct clamping region of the blade and/or in a region adjacent thereto is constructed to be flexible in the direction transverse to the blade but relatively rigid in the direction of the blade's width in order to guarantee as free a deformation of the blade as possible over its entire width. By contrast the foot region of the holding bar, which is used for fixing to a fastening base, is constructed to be rigid. The holding bar usually includes several individual parts, together forming an integrated unit, which are arranged separate from the actual support beam of the doctor device but on it.
From DE 296 01 342 U1 there is also known a doctor unit with a holding bar and a doctor element fitted thereto, wherein said element can be placed against or inserted into a support beam by way of mutually matching support faces. In this case provision is made for an apparatus with which a holding force can be applied, thus pulling or sucking the holding bar against the support beam when it is placed against or inserted into the support beam by way of the support faces. The apparatus is constructed such that the holding force can be deactivated and reactivated.
In addition, from DE 39 40 450 A1 there is known a doctor device equipped with a seat for a leaf spring, which either acts as a doctor element or is connected thereto and which in its region away from the coating edge of the doctor element can be clamped in place by a clamping element which presses the leaf spring against a support face. In the clamping region provision is made on the seat of the leaf spring for a duct running parallel to the coating edge, wherein a series of vibration pulse transmitters is arranged along the length of the duct and enables cleaning of the blade seat. By using vibrations to remove any adhering residues of the coating medium it is intended to guarantee that the coating blade sits correctly in its clamping arrangement.
The devices known hitherto often provide only poor possibilities for cleaning because the interior space is impossible to view and difficult to reach. This results in a great servicing effort because numerous parts have to be dismantled in order to reach inner lying parts for cleaning.
What is needed in the art is a doctor device which is simple in design and provides optimum access to all functional parts for cleaning or servicing and can be quickly dismantled and reassembled.